Radioisotope labeling of biological compounds is a powerful tool used in many medical research techniques. Tritium is an especially useful radioisotope since it can be used to label many biologically active materials. For example immunologists use tritiated thymidine which can be incorporated into the DNA molecules of growing cells. This provides an accurate way to monitor cell growth. Thus tritium labeling has become one of the most important techniques for performing cell growth assay measurements which are a vital part of cancer research. The techniques for detecting tritium are well developed but they are tedious, time consuming, and potentially hazardous. The difficulties stem from the present need to use liquid scintillation fluids coupled to photomultiplier tubes to detect the tritium beta particles. To overcome these difficulties, we propose to investigate the use of a new solid state sensor as a beta detector which will greatly simplify the tritium measurement and offers the potential for automation. The benefits of this approach include reduced manpower requirements, simplified testing procedures, lowered instrument cost, the ability to keep a permanent experimental record of the assay since the technique is nondestructive, and reduced radioactive waste.